Apex domains cannot have CNAME records.
Question and response
Question
dig customer.tdatabrasil.net.br. NS
Answer
customer.tdatabrasil.net.br. 5 NS te-br-spo-ib-dns2.tdatabrasil.net.br.
customer.tdatabrasil.net.br. 5 NS te-br-spo-tic-dns1.tdatabrasil.net.br.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0